Security camera systems

ABSTRACT

A security camera system is provided. Several video cameras operate in conjunction with an image display monitor, a user control and camera selector means whereby a target of interest may be followed. Each two cameras providing adjacent areas of coverage are operable to provide an overlay image portion at transition regions of a displayed image. Upon movement of the target of interest to a specified transition region of a currently displayed image provided by one video camera, the camera selection means is operable to select a second camera whereby to maintain target display continuity by the monitor.

This invention relates to security camera systems and more especiallybut not exclusively it relates to camera systems of the kind used inshopping precincts or urban centres to provide video surveillance.

Camera systems providing video surveillance are in common use and maycomprise a large number of cameras in order to provide adequate videosurveillance of a prescribed area. If an incident occurs, security staffin ‘closed circuit television’ (CCTV) control rooms, will attempt tokeep a person involved in the incident, and who might be making haste toleave the scene, within the field of view. This might involve switchingbetween cameras, as the person leaves the field of view of one cameraand enters the field of view of another camera or cameras, so that thecamera used is always the one which affords the best view of the personbeing observed. In practice, this can be difficult, requiring highlytrained staff who are familiar with the camera layout on a particularsite. It is therefore all too easy to lose track of a person, even on asite having good camera coverage, and this may result in the loss ofvital evidence, since video surveillance data used for prosecution istypically required to be continuous in time.

It is an object of this invention to provide an improved camera systemwherein the tracking of a person moving between areas covered bydifferent security cameras is facilitated whereby the task of securitystaff is simplified.

In accordance with a further aspect of the invention, there is provideda security camera system comprising a plurality of video cameras, animage display monitor, a user control and camera selector means; whereinthe cameras' images in combination can provide a predetermined overallarea of coverage; wherein a target of interest can be observed by afirst video camera and an image of said target be displayed on themonitor; characterised in that overlap image portions at transitionregions of a displayed image are provided by two adjacent cameras, eachsuch transition region being displayed as a ‘button’ region by the imagedisplay; wherein there are a plurality of such ‘button’ regions beingarranged about or surround a central area in an image in a field ofview; wherein, upon movement of the target to a transition region, theuser control is operable to select the ‘button’ region of an imagedisplayed, whereby to select a second camera and to employ video signalsfrom the second video camera to maintain target image continuity.

The user control may comprise a mouse or a like device to control acursor which is operable to indicate when the target has moved to animage transition region. Alternatively or additionally a touch sensitivescreen may be provided.

The user control may be used to select a transition region displayed bythe image display monitor, from a plurality of such regions which arearranged to surround an image displayed, and which are also arrangedwithin the image, the transition region selected indicating an imageregion of a currently displayed image approached by a target, independence upon which transition region selection, video signals fromanother of the video cameras are used thereby to maintain target displaycontinuity by the monitor.

Conveniently the user control includes a CPU, which is operable to storedata including, in respect of each camera, the pixel positions of thelines at which transitions occur, and the identity of the camera to beselected at that transition. The data stored in the CPU may include, forexample, in respect of each camera: image centre data, focal lengthdata, and distortion parameters. At least some of the cameras may befixed and/or at least some of the cameras may be pan-tilt-zoom (PTZ)cameras. The CPU may include image processing software which operates torecognise the character of an image by comparing it for correspondencewith a plurality of stored reference images, in dependence upon whichcomparison, the CPU operates for camera selection.

The CPU may include image processing software which operates torecognise a character in an image by comparing key features of the imagefor correlation with key features in a plurality of stored referenceimages in dependence upon which comparison the CPU operates for cameraselection.

In one embodiment the features along one or more co-ordinates of animage may be compared for correlation with the features of one or morecorresponding co-ordinates of a reference image.

The video camera may be a thermo-sensing camera such as an infra-redcamera.

In accordance with a further aspect of the invention, there is provideda security camera system, a method of operating a security camera systemcomprising a plurality of video cameras, an image display monitor, auser control and camera selector means; wherein the cameras' images incombination can provide a predetermined overall area of coverage;wherein a target of interest can be observed by a first video camera andan image of said target be displayed on the monitor; wherein overlapimage portions at transition regions of a displayed image are providedby two adjacent cameras, each such transition region being displayed asa ‘button’ region by the image display; wherein there are a plurality ofsuch ‘button’ regions being arranged about or surround a central area inan image field of view; wherein, upon movement of the target to atransition region, the user control is operable to select the ‘button’region of an image displayed, whereby to select a second camera and toemploy video signals from the second video camera; the method comprisingthe steps of: observing a target of interest displayed as an image onthe monitor; characterised in that upon movement of the target to atransition region, operating the camera selection means whereby an imagefrom a second camera is displayed, whereby target image continuity maybe maintained. The user control may comprise a mouse or a like operativedevice operable to control a cursor which can be used to track thetarget and to indicate when it has moved to an image transition region.

One embodiment of the invention will now be described by way of exampleonly with reference to accompanying drawings wherein;

FIG. 1, is a schematic block diagram of a security camera system usingfixed cameras and,

FIG. 2, is a schematic block diagram of a security camera system usingfixed cameras and PTZ cameras wherein parts corresponding to those shownin FIG. 1 bear the same numerical designations.

Referring now to FIG. 1, an exemplary security camera system is shown,of the kind used in shopping precincts or urban centres to provide videosurveillance comprises a plurality of fixed security cameras 1, 2, 3, 4,which are arranged to feed their respective video signals to a cameramatrix 5. The camera matrix 5, serves as a video camera selector, toselect the signals from one of the cameras 1, 2, 3, 4, for display onthe screen of an image display monitor 6, which is operativelyassociated with a user interaction device 7. The device 7, mightconveniently comprise a mouse or the like which can be used to move acursor 8, around an image display 9, on the display monitor 6. Insteadof there being a memory means associated with the matrix (controlselection means), there is provided a separate CPU which receivessignals from the camera matrix relating to all the signals from thecameras. The camera matrix 5, is controlled by the CPU in which data isretained relating to a fixed field of view afforded by each of thecameras 1, 2, 3, 4, and the position of the cursor 8. In operation, atarget person, for example, may be visually followed by an operatoracross a current image field of view and when the target approaches anedge of the field of view, the device 7 may be used to ‘mark’ the spotwith the cursor 8, for example by ‘clicking’ on the boundary. Dataidentifying the marked spot together with data appertaining to eachavailable camera image is then processed in the CPU in order to selectthe most suitable camera to feed the monitor 6.

In an alternative embodiment the image displayed may be surrounded by‘button regions’ 11, the ‘button region’ (or regions) adjacent to a spotwhereat a target approaches the limit of an image being selected usingthe cursor 8, and the device 7, in order to provide information for theCPU to facilitate selection of an appropriate one of the cameras 1, 2,3, or 4 for the image display 9.

In a still further embodiment, the screen may be equipped with a touchsensitive screen, whereby the camera is selected following the placingof a finger, for example, upon a touch sensitive portion of the screen.

Referring now to FIG. 2, in an alternative arrangement PTZ cameras 12,13, and 14, are used in addition to the fixed cameras 1, 2, 3, 4. Inthis arrangement data is stored in the CPU appertaining to variousparameters relating to the image produced by each of the PTZ cameras 12,13, 14, to facilitate image processing in the CPU in order to determinethe relationship of each image, to other images, to the overall displaycoverage and to the cursor and/or button positions, whereby adetermination in the CPU of the most appropriate camera to use isfacilitated.

Considering now some applications, it will be appreciated that a systemaccording to this invention would enable security staff to track asuspect target through the images provided by a set of video cameras,using both PTZ cameras and/or fixed cameras or, indeed, to have a systemhaving logic operable to track an identified target. It is apparent thatwith fixed cameras, the problem is comparatively easily solved byknowledge of the transition regions in each camera where the subjectleaves the field of view, and of the camera on which that region cannext be seen.

Alternatively, if a point in one image is selected, all other cameras onwhich that point can be seen, could be displayed, for example, aswindows on a PC display. The security staff would then be capable oftracking a target individual by ‘clicking’ on the current image view ata point where the target individual goes off the edge of the scene, soas to prompt the provision a fresh display provided by the best one ofthe other cameras to which the target is visible.

For PTZ cameras the problem is somewhat more complex, but isnevertheless soluble. In existing camera installations, it is unlikelythat the PTZ cameras will have feedback of the values of pan, tilt andzoom available to the PC. This information, or some equivalentinformation, is necessary to determine on which new cameras a targetwill be visible when leaving the field of view of a current camera. Thisinformation can however be measured, as herein before explained, byusing image processing. This method requires comparison of a currentimage with a set of stored reference images to determine where thetransition regions occur in the current image. This could be done inreal-time whilst a camera was being moved by operation of it joystickcontrol, to determine its current PTZ parameters. With the use of asmart CPU, the functions of a user control could be reduced to that ofselecting a target.

1. A security camera system comprising: a plurality of video cameras; animage display monitor; a user control; and camera selector means;wherein the cameras' images in combination can provide a predeterminedoverall area of coverage; a target of interest can be observed by afirst camera and an image of said target be displayed on the monitor; animage acquired by said first camera overlaps with an adjacent imageacquired by at least one other camera, forming a transition region, saidtransition region being defined by a portion that is common to theimages of both said first camera and said at least one other camera;each such transition region is displayed as a ‘button’ region by theimage display; there are a plurality of such ‘button’ regions whichsubstantially surround a central portion of an image in a field of view;and upon movement of the target to a transition region, the user controlis operable to select the ‘button’ region in which the target appears ina displayed image, so as to select a second camera and to employ videosignals from the second video camera to maintain target imagecontinuity.
 2. A security camera system as claimed in claim 1, whereinthe user control comprises a device operable to control a cursor whichcan be used to track the target and to indicate when it has moved to animage transition region.
 3. A security camera system as claimed in claim1 wherein the user control comprises a touch sensitive screen.
 4. Asecurity camera system as claimed in claim 1, wherein the user controlincludes a CPU and wherein the CPU is operable to store data including,for example, in respect of each camera: image center data, focal lengthdata distortion parameters, and x,y,z, and pan and tilt data.
 5. Asecurity camera system as claimed in claim 1, wherein at least some ofthe cameras are fixed.
 6. A security camera system as claimed in claim1, wherein at least some of the cameras are PTZ cameras.
 7. A securitycamera system as claimed in claim 6, wherein the CPU includes imageprocessing software for PTZ cameras, which software operates torecognize the character of an image by comparing it for correspondencewith a plurality of stored reference images, in dependence upon whichcomparison the CPU operates for camera selection.
 8. A security camerasystem as claimed in claim 7, wherein the CPU includes image processingsoftware which operates to recognize the character of an image bycomparing key features of the image for correspondence with key featuresin a plurality of stored reference images in dependence upon whichcomparison the CPU operates for camera selection.
 9. A security camerasystem as claimed in claim 8, wherein key features along one or moreco-ordinates of an image are compared for correspondence with the keyfeatures along one or more corresponding co-ordinates of a referenceimage.
 10. A security camera system as claimed in claim 6, wherein thedata stored in the CPU includes in respect of each camera, the pixelpositions of lines at which transitions occur, and the identity of acamera to be selected at that transition.
 11. A security camera systemas claimed in claim 1, wherein the video camera is an infra-red camera.12. A method of operating a security camera system comprising aplurality of video cameras, an image display monitor, a user control anda camera selector means; wherein, the cameras' images in combination canprovide a predetermined overall area of coverage; a target of interestcan be observed by a first camera and an image of said target can bedisplayed on the monitor; an image acquired by said first cameraoverlaps with an adjacent image acquired by at least one other camera,forming a transition region, said transition region being defined by aportion that is common to the images of both said first camera and saidat least one other camera; each such transition region is displayed as a‘button’ region by the image display; there are a plurality of such‘button’ regions which substantially surround a central portion of animage field of view; and upon movement of the target to a transitionregion, the user control is operable to select the ‘button’ region inwhich the target appears in a displayed image, whereby to select asecond camera and to employ video signals from the second video camera;the method comprising the steps of: observing a target of interestdisplayed as an image on the monitor; and upon movement of the target toa transition region, operating the user control to select the button inwhich the target appears, whereby said camera selector means causes animage from a second camera to be displayed so that target imagecontinuity may be maintained.
 13. The method according to claim 12,wherein the user control comprises a mouse or the like operative tocontrol a cursor which is operable to track the target and to indicatewhen it has moved to an image transition region.
 14. The method asclaimed in claim 12 wherein the user control comprises a touch sensitivescreen.
 15. The method according to claim 14, wherein: the user controlis operable to select a ‘button’ region displayed by the image displaymonitor, from a plurality of such regions which are arranged about orsurround an image displayed, the ‘button’ region selected indicating aparticular transition region of a currently displayed image approachedby the target; and dependent upon a particular ‘button’ regionselection, video signals from another of the video cameras are usedthereby to maintain target display continuity by the monitor.
 16. Themethod as claimed in claim 14, wherein the user control is operable toselect a transition region displayed by the image display monitor, froma plurality of such regions which are arranged about or surround animage displayed, the transition region selected indicating an imageregion of a currently displayed image approached by a target, independence upon which transition region selection, video signals fromanother of the video cameras are used, thereby to maintain targetdisplay continuity by the monitor.